In order to fulfill the increasing demand for renewable energy, besides the lithium-ion batteries, other alkali (Na, K)-ion batteries are extensively investigated. However, the difficulty to find ...universal and environmentally benign electrodes for these alkali (Na, K)-ion batteries still severely restricts their development. Promising characteristics, including molecular diversity, low cost, and operation safety, endow the organic electrodes more advantages for applications in alkali-ion batteries. However, organic electrodes usually deliver a reversible capacity smaller than that of their inorganic counterparts due to sluggish ion/electron diffusion and possible dissolution in organic electrolytes. This work introduces fluorine atoms into the covalent triazine frameworks (CTF) to obtain two-dimensional layered fluorinated CTF (FCTF) and its exfoliated few-layered product (E-FCTF) and uses them as anodes of Li, Na, and K organic batteries. Exfoliated E-FCTF electrode delivers high reversible capacities, as well as excellent cycle life for alkali organic batteries (1035 mAh g–1 at 100 mA g–1 after 300 cycles and 581 mAh g–1 at 2 A g–1 after 1000 cycles for lithium organic batteries). In view of the experimental probing and the theoretical calculation, the Li storage mechanism for the E-FCTF can be determined to be an intriguing multielectronic redox reaction originated from lithium storage on the benzene ring and triazine ring units.
Metal–organic frameworks (MOFs) and relative structures with uniform micro/mesoporous structures have shown important applications in various fields. This paper reports the synthesis of unprecedented ...mesoporous NixCo3−xO4 nanorods with tuned composition from the Co/Ni bimetallic MOF precursor. The Co/Ni‐MOFs are prepared by a one‐step facile microwave‐assisted solvothermal method rather than surface metallic cation exchange on the preformed one‐metal MOF template, therefore displaying very uniform distribution of two species and high structural integrity. The obtained mesoporous Ni0.3Co2.7O4 nanorod delivers a larger‐than‐theoretical reversible capacity of 1410 mAh g−1 after 200 repetitive cycles at a small current of 100 mA g−1 with an excellent high‐rate capability for lithium‐ion batteries. Large reversible capacities of 812 and 656 mAh g−1 can also be retained after 500 cycles at large currents of 2 and 5 A g−1, respectively. These outstanding electrochemical performances of the ternary metal oxide have been mainly attributed to its interconnected nanoparticle‐integrated mesoporous nanorod structure and the synergistic effect of two active metal oxide components.
Microwave‐assisted one‐step formation of bimetallic Co/Ni‐metal–organic framework‐74 is used to fabricate a mesoporous Co–Ni–O nanorod, which delivers higher‐than‐theoretical reversible capacities, with excellent high‐rate performances for lithium‐ion batteries.
A unique CuO@NiO microsphere with three-layer ball-in-ball hollow morphology is successfully synthesized by Cu–Ni bimetallic organic frameworks. The beforehand facile microwave-assisted production of ...the Ni organic framework sphere is used as the template to induce the morphology control of bimetallic oxides. Designed by the controlled surface cationic exchange reactions between Cu and Ni ions, there is an elemental gradient (decreased amount of CuO but increased amount of NiO) from the shell to the core of the microsphere product. This ternary metal oxide hollow structure is found to be very suitable for solving the critical volume expansion problem, which is critical for all high-capacity metal oxide electrodes for lithium ion batteries. A reversible larger-than-theoretical capacity of 1061 mAh·g–1 can be retained after a repetitive 200 cycles without capacity fading compared to the initial cycle. These excellent electrochemical properties are ascribed to the step-by-step lithium insertion reactions induced by the matched CuO@NiO composition from the shell to the core and facilitated lithium/electron diffusion and accommodated volume change in the porous bimetallic oxides microsphere with a multiple-layer yolk–shell nanostructure.
In order to improve the data retrieval accuracy of preschool education major curriculum, this paper designs an auxiliary teaching system for preschool education specialty courses based on artificial ...intelligence. 2000 preschool education teachers and 3000 students in M city were selected to conduct a questionnaire survey to analyze the application status of artificial intelligence technology, advantages and disadvantages of assisted teaching, obstacles and training intentions of assisted teaching, and the impact on the personal development of teachers and students. Using artificial intelligence technology to improve the shortcomings of existing preschool education professional courses, through the Vue.js technology in the artificial intelligence method to achieve the MVVM mode sharing of preschool education professional courses, using MySQL database to achieve multiuser multithread operation of preschool education system, using MySQL data to complete data storage, C# was used as the programming language to design the learning module of preschool education professional courses, and the artificial intelligence-based preschool education professional course auxiliary teaching system was designed. The experimental results show that when the retrieval quantity of curriculum resources is 600 GB, the response time of resource retrieval of the designed system is 7 s, and the retrieval accuracy of curriculum data of education major can reach 95%. The performance of the system is good.
Organic electrodes for low-cost potassium ion batteries (PIBs) are attracting more interest by virtue of their molecular diversity, environmental friendliness, and operation safety. But the sluggish ...potassium diffusion kinetics, dissolution in organic electrolyte, poor electronic conductivity, and low reversible capacities are several drawbacks compared with inorganic counterparts. Herein, the boronic ester based covalent organic framework (COF) material is successfully prepared on the exterior surface of carbon nanotubes (CNTs) via rational design of the organic condensation reaction and used as an anode material for PIBs. The few-layered structure of COF-10@CNT can provide more exposed active sites and fast K+ kinetics. It exhibits ultrahigh potassium storage performances (large reversible capacities of 288 mAh g–1 after 500 cycles at 0.1 A g–1 and 161 mAh g–1 after 4000 cycles at 1 A g–1), which is superior to previous organic electrodes and most inorganic electrodes. Moreover, the K-storage mechanism is proposed to be π-cation interaction between K+ and conjugated π-electrons of benzene rings.
•This paper proposes a simple and effective spatial-spectral (SESS) method.•SESS fuses spectral and multi-scale spatial features of coastal wetlands.•SESS achieves better classification results than ...other state-of-the-art methods.•The first paper to use China ZY1-02D satellite data in mapping coastal wetlands.
This paper proposes a simple and effective spatial-spectral (SESS) method for mapping large-scale coastal wetlands using China ZY1-02D satellite hyperspectral data. First, the improved sparse subspace clustering algorithm is implemented to select presentative bands, and then the multi-scale low-rank decomposition algorithm is employed to extract multi-scale spatial features. After that, the extracted spatial and selected spectral features are stacked and fused using presented Landmark-neighborhood preserving embedding algorithm. Finally, the low-dimensional fused features are classified with two popular classifiers (i.e., random forest and support vector machine) to map coastal wetlands. Experiments results show that the SESS obtains the highest classification accuracy of 96.92% and 94.84% on Yellow River Delta and Yancheng coastal wetlands of China, respectively, exhibiting good capability in accurately identifying complicated ground objects. This paper is the first attempt to investigate the potentials of China ZY1-02D satellite hyperspectral data, and the SESS can also be applied into other hyperspectral data.
Selecting and assembling metal ions and bridging ligands can fabricate two-dimensional metal-organic framework nanosheets, which can act as prospective materials for efficient energy applications. ...Thanks to large surface area and more porosity, ultrathin 2D MOFs nanosheets and their derived two-dimensional nanosheet materials exhibit more highly approachable active sites uncovered on the surface, decreased ion diffusion distance and fast electron transfer for energy storage/conversion applications. Herein, this review will summarize the latest developments with discussion of design, fabrication, energy storage as well as conversion performance of 2D MOFs and their-derived two-dimensional materials. Moreover, the development of exfoliated two-dimensional MOFs and their derivatives, as well as the promising trends and prospects in application as excellent-performance electrode materials in batteries, supercapacitors, and electrocatalysis are also present.
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•Recent developments of 2D MOF materials for energy applications are reviewed.•Design strategies of 2D MOF related materials are summarized.•Relationship between the structure and performance is discussed in details.•Future research tendency of 2D MOF-related materials is highlighted.
Aiming at the problems of high redundancy and slow integration speed in the existing education resource data integration methods, a new preschool language education resource integration method based ...on metadata warehouse is designed. The metadata warehouse is designed, and the advantages of the integrated database are analyzed. On this basis, the sample data of preschool language education resources are classified with the help of cost matrix, and the constraints of different types of classification are set. The data collector of preschool language education resources is set up by using random forest algorithm to complete the data collection of preschool language education resources. The data of preschool language education resources are processed consistently, and the convergence of the data is calculated by edge function. On this basis, the redundant data in preschool language education data resources are characterized with the help of discourse, and the redundant data are removed to complete the data preprocessing of preschool language education resources. We determine the dimension distance between preschool language education resource data and complete the clustering integration of preschool language education resource data with the help of fuzzy mean clustering algorithm. The experimental results show that the integration method designed in this paper can reduce the redundancy in the integrated data, and the integration speed is fast.
A sparse and low-rank near-isometric linear embedding (SLRNILE) method has been proposed to make dimensionality reduction and extract proper features for hyperspectral imagery (HSI) classification. ...The SLRNILE stands on the theory of the John-Lindenstrauss lemma, and tries to estimate a sparse and low-rank projection matrix that satisfies the restricted isometric property (RIP) condition on all secants of the HSI data. The RIP condition guarantees that the desired linear mapping near-isometrically preserves nearest neighbor points of all HSI pixels. Seeking the desired mapping is then modeled into minimizing a Lagrange multipliers formulation. The alternating direction method of multipliers framework is utilized to solve the above convex program, and column generation techniques are adopted to alleviate the computation memory burden during the optimization procedure. Five experiments on three widely used HSI data sets are designed to completely test the performance of SLRNILE, and experimental results are compared against those of six state-of-the-art feature extraction methods, including principal component analysis, Laplacian eigenmaps, locality preserving projections, neighborhood preserving embedding, sparse nonnegative matrix underapproximation, and random projections. The results show that SLRNILE performs best among all the seven methods, and its computational time is longest of all but still bearable for regular users. Therefore, the SLRNILE can be a good choice for feature extraction in HSI classification.
Conjugated polymeric molecules have been heralded as promising electrode materials for the next-generation energy-storage technologies owing to their chemical flexibility at the molecular level, ...environmental benefit, and cost advantage. However, before any practical implementation takes place, the low capacity, poor structural stability, and sluggish ion/electron diffusion kinetics remain the obstacles that have to be overcome. Here, we report the synthesis of a few-layered two-dimensional covalent organic framework trapped by carbon nanotubes as the anode of lithium-ion batteries. Remarkably, upon activation, this organic electrode delivers a large reversible capacity of 1536 mAh g
and can sustain 500 cycles at 100 mA g
. Aided by theoretical calculations and electrochemical probing of the electrochemical behavior at different stages of cycling, the storage mechanism is revealed to be governed by 14-electron redox chemistry for a covalent organic framework monomer with one lithium ion per C=N group and six lithium ions per benzene ring. This work may pave the way to the development of high-capacity electrodes for organic rechargeable batteries.
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